Gage maintaining arrangement for drill bit cutters



E. G. BOICE June 1, 1965 GAGE MAINTAINING ARRANGEMENT FOR DRILL BIT CUTTERS Filed Feb. 9. 1961 Y yu INVENTOR.

ATTORNEY! United States Patent f 3,186,500 GAGE MAINTADIING ARRANGEMENT FGR DRILL BET CUTTERS Elvin G. Boice, Houston, Tex., assignor to Reed Boiler Bit Company, Houston, Tex., a corporation of Texas Filed Feb. 9, 1961, Ser. No. 88,218 7 Claims. (Cl. 175-374) This invention relates generally to roller drill bits and more particularly to gage maintaining means for rock bit cutters.

In the rotary drilling of bores in earth formations, a roller drill bit is connected to a lower end of a hollow drill stem which is lowered and rotated to cause the bit rollers to roll upon the bottom of a borehole to cut or crush the formation being encountered. A drilling fluid such as air or liquid is circulated downwardly through the drill stem and bit, and rises to the surface of the earth in the space between the drill stern and the wall of the hole. The drilling fluid thus circulating serves to cool the drill bit, and carry out of the borehole cuttings produced by the drilling operation. The drill bit rollers have bottom cutting portions and gage or wall engaging portions to produce a uniform diameter well bore.

A general object of this invention is to provide a new and improved roller cutter for rotary drill bits.

Another object is to provide a new and improved gage maintaining means for a roller cutter.

Another object is to provide movable hard metal inserts in the gage portion of the rock bit cutter.

Another object is to provide hard metal balls rotatably retained in sockets in the gage face of a rock bit cutter.

Other objects will become apparent from the following description and accompanying drawings, wherein:

FIG. 1 is a side elevational View of a drill bit embodying the invention.

FIG. 2 is a sectional view taken along line 22 in FIG. 1. i

FIG. 3 is an enlarged fragmentary view taken along line 33 in FIG. 2.

FIG. 4 is an enlarged fragmentary view of a drill bit cutter showing another embodiment of the invention.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.

Referring to the drawings,'a steel drill bit is shown generally at 1 comprising a head 2 and a hollow threaded pin 3 extending upwardly for attachment to a lower end of a drill stem (not shown). The head 2 has a plurality of downwardly extending legs 4 which terminate in downwardly and inwardly extending shafts 5. Steel roller cutters 6, 7 and 8 are rotatably mounted on the shafts 5.

As shown in FIG. 2, a suitable bearing structure is provided comprising roller bearings 9 and ball bearings 10 disposed in complemental raceways on the shafts 5 and in the cutter 6. The inner end of the shaft 5 is reduced to provide a friction bearing pin 11. The ball bearings 10 are inserted in place through an opening 12 in the leg 4 and the shaft 5. A ball retaining plug 13 is then inserted into the opening 12 and secured in place by weld 14. V

outside diameter of the inserts 15.

Each of the roller cutters 6, 7 and 8 has a second frusto-conical gage face portion 17 which is adapted to confront the lower portion of the wall of a borehole as the cutter rotates on the shaft 5. The gage face portion 17 has a circular raceway, or groove, IStherein which is 3,186,509 Patented June 1, 1965 supplied with a plurality of sintered tungsten carbide balls 19 movable therein and arranged to protrude outwardly beyond the surface of the gage face portion 17.

Referring to FIG. 2, the cutter 6 may have a bore 20 disposed to intersect the raceway 18. The carbide balls 19 are then inserted through the bore 20 into the raceway 18 after which a retaining plug 21 is inserted into the bore 20 and secured by a weld 22. The width of the raceway 18 at the surface 17 is smaller in dimension than the diameter of the balls 19 in order to retain the balls within said raceway. It will be apparent that as the cutter 6 rotates on the shaft 5, a given point on the surface 17 will intermittently confront and engage the lower portion of the wall of the borehole to produce and maintain the desired bore diameter. The action of the gage face portion on the wall of a borehole is a scraping action which subjects the gage portion 17 to extreme abrasive wear by the formation. .It is desirable that a uniform diameter borehole is maintained throughout so that subsequent drill bits or other equipment may be lowered into the borehole without having to ream the bore to the desired diameter.

By supplying the hard metal balls 19 in the surface 17, I achieve protection for the gage. face of a drill bit roller, and improved gage maintaining results. Since the balls 19 are free to move or circulate in the raceway 18, the balls may roll rather than scrape on the wall of the hole to crush the formation. The spherical shape is ideal for this action since it is very strong and the operating stresses thereon are in compression.

The resulting stress through the balls 19 will be on the inboard surface of the raceway 18 which, beingmade of steel, may be carburized to resist wear of the races 18 by the balls 19. In operation, even if the balls 19 do not circulate freely within the raceway 18, because of the presence of formation cuttings or other detritus, the balls 19 have a tendency to rotate because of the rolling action on the wall of the borehole, thus the balls 19 may present new wear surfaces as drilling progresses. In other words, the balls 19 may be exposed to wear about their entire surface, thus providing more effective area to maintain the gage of the borehole.

All of the balls 19 may be composed of a wear resistant material such as sintered tungsten carbide. However, if desired, hardened steel balls or the like may be interposed alternately between the tungsten carbide balls 19.

Referring to FIGS. 4 and 5, another embodiment of the invention is shown wherein the cutter 6' has a gage surface 17' which has a plurality of spaced sockets 23 into which are disposed hard metal balls 24. After the balls 24 are disposed in the sockets 23, the material of the gage face 17 is deformed, as by staking, around the lip of the socket to retain the ball 24 in the gage face 17. The balls 24 are arranged so that they may rotate within the sockets 23 during the drilling operation.

The invention is not limited to the embodiments shown. Various changes within the scope of the following claims will occur to those skilled in the art.

I claim:

1. In a well drill, a bit head having a plurality of downwardly extending legs, an inwardly and downwardly extending shaft on each of said legs, a roller cutter rotatably mounted on each of said shafts, a first frusto-conical portion on said roller cutter having cutting elements adapted to drill the bottom of a borehole, a second frusto-conical gage face portion on said roller cutter adapted to confront the lower portion of the Wall of said borehole as the said cutter rotates on its said shaft, the said gage face portion having an outwardly open circular raceway therein coaxial with the axis of said cutter, a plurality of sintered tungsten carbide balls movable in said raceway and arranged to protrude outwardly beyond the surface of said gage face portion, means through which said balls are inserted into said raceway, and means to retain said balls in said raceway.

2. In a well drill, a bit head having a plurality of downwardly extending legs, an inwardly and downwardly extending shaft on each of said legs, a roller cutter rotatably mounted on each of said shafts, a first frusto-conical portion on said roller cutter having cutting elements adapted to drill the bottom of a borehole, a second frusto-conical gage face portion on said roller cutter arranged to confront the lower portion of the wall of said borehole as the said cutter rotates on the said shaft, the said gage face portion having an outwardly open circular raceway therein coaxial with the axis of said cutter, a plurality of tungsten carbide inserts movable in said raceway arranged to protrude outwardly beyond the surface of said gage face portion, and means to retain said inserts in said raceway.

3. In a well drill, a bit head having a plurality of downwardly extending legs, an inwardly and downwardly extending shaft on eachof said legs, a roller cutter ro tatably mounted on each of said shafts, a first frustoconical portion on said roller cutter having cutting elements adapted to drill the bottom of a borehole, a second frusto-conical gage face portion on said roller cutter arranged to confront thelower portion of the wall of said borehole as the said cutter rotates on the said shaft, the said gage face portion of at least one of the cutters having an outwardly open circular raceway therein coaxial with the axis of said cutter, a plurality of sintered tungsten carbide balls movable in said raceway and arranged to protrude outwardly beyond the surface of said gage face portion, and means to retain said balls in said raceway. I a

4. In a well drill, a bit head having a plurality of downwardly extending legs, an inwardly and downwardly extending shaft on each of said legs, a roller cutter rotatably mounted on each of said shafts, a frusto-conical having a circumferential groove therein, a plurality of wear resistant balls movable in said groove and arranged to protrude outwardly beyond the surface of said gage face portion, means through which said balls are inserted into said groove, and means to retain said halls in said groove.

5. In a well drill, a bit head having a plurality of downwardly extending legs, an inwardly and downwardly extending shaft on each of said legs, a roller cutter rotatably mounted on each of said shafts, a frusto-conical portion on said roller cutter having cutting elements adapted to drill the bottom of a borehole, a gage face portion on said roller cutter arranged to confront the lower portion of the wall of said borehole as the said cutter rotates on the said shaft, the said gage face portion having a groove therein, a plurality of tungsten carbide inserts movable in said groove and arranged to protrude outwardly beyond the surface of said gage face portion, means through which said inserts are supplied into said groove, and means to retain said inserts in said groove.

6. A rotary drill cutter for a rock bit comprising a bottom cutting portion and a gage face, the said gage face having a groove therein, sintered tungsten carbide balls movable in said groove, and arranged to protrude from the surface of said gage face means through which said balls are inserted into said groove, the width of the groove at the surface of said gage face being smaller in dimension that the diameter of said balls.

7. A rotary drill cutter having a gage face, the said gage face having a groove therein, and tungsten carbide inserts movable in said groove and arranged to protrude from the surface of saidgage face, means through which said inserts are supplied into said groove, and means to retain said inserts in said groove.

References Cited by the Examiner UNITED STATES PATENTS 474,297 5/92 Hoffman -331 X 1,725,298 8/29 Pickin 175-371 X 2,176,358 10/39 Pearce 175-371 X 2,260,487 10/41 Scott 175-371 X 2,579,268 12/51 Malherbe 175-410 2,597,669 5/52 Pilon 175-374 X 2,626,128 1/53 Boice 175-374 2,774,571 12/56 Morlan 175-374 X 2,939,684 6/60 Payne 175-375 2,951,683 9/60 *Tilden 175-332 X CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner. 

7. A ROTARY DRILL CUTTER HAVING A GAGE FACE, THE SAID GAGE FACE HAVING A GROOVE THEREIN, AND TUNGSTEN CARBIDE INSERTS MOVABLE IN SAID GROOVE AND ARRANGED TO PROTRUDE FROM THE SURFACE OF SAID GAGE FACE, MEANS THROUGH WHICH SAID INSERTS ARE SUPPLIED INTO SAID GROOVE, AND MEANS TO RETAIN SAID INSERTS IN SAID GROOVE. 